Port 5938 TeamViewer · TCP

What runs on port 5938

TeamViewer. Outbound only in normal use: the client connects to TeamViewer's servers on 5938 (falling back to 443 and 80), so nothing needs to be open inbound. Seeing it inbound on a firewall is unexpected; seeing it outbound on a server may be unexpected too.

Software that uses it: TeamViewer

Should port 5938 be open?

Designed to face the internet. This port exists to be reachable from anywhere, so the usual question is not whether to open it but how the service behind it is configured and patched.

• Blocking outbound 5938 does not stop it; it falls back to 443. Use application control if you need to block it.

Check port 5938

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :5938'
sudo lsof -i :5938

# from another machine: is it reachable?
nc -zv host 5938
nmap -p 5938 host
curl -v telnet://host:5938      # raw TCP connect test, Ctrl-C to leave

A port that answers from the internet when it should not is the finding; nmap from a machine outside your network (or a VPS) is the honest test, because scans from inside the LAN pass the firewall you are trying to verify.

Allow or block port 5938

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 5938 proto tcp
sudo ufw deny 5938/tcp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 tcp dport 5938 accept
nft add rule inet filter input tcp dport 5938 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 5938 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 5938 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=5938 protocol=tcp accept'

Replace 10.0.0.0/8 with the networks that need access. Allowing by source address is the rule that matters; "allow 5938" with no source is just "open".

Related ports

• 3389 RDP — Windows Remote Desktop
• 5900 VNC — Remote desktop

Part of the port number reference. Ports are 16-bit numbers; see also the subnet calculator and the packet decoder, which shows ports inside TCP and UDP headers.

Questions